EP1555238B1 - Trolley with a drive - Google Patents

Description

The invention relates to a truck with drive according to the preamble of claim 1 or 2.

Such a truck is already out of the US-A-4,431,084 known.

With industrial trucks, especially pallet trucks, a distinction is made with regard to the wheel assembly between tricycles, four-wheeled or five-wheeled vehicles. In three-wheeled vehicle two wheels are formed as load wheels of radarmgestützten pallet trucks or as front wheels of so-called counterbalance trucks. In the rear area only a drive wheel is mounted, which is also pivotable for steering purposes about a vertical axis. In four-wheel vehicles are located at the front and rear ends of two wheels or rollers, such as load wheels in the Radarmen, a drive wheel at the opposite end in the corner and next to a support role. Again, the drive wheel for steering purposes is pivotable about a vertical axis. In five-wheel vehicles, the steered drive wheel is located approximately in the middle of the drive part of the truck, and on both sides of the drive wheel in each case a support roller is freely pivotally mounted about a vertical axis.

1. 1. Dreiradfahrwerk - statisch bestimmt:
   • 1.1 alle Räder sind vertikal unbeweglich mit dem Rahmen verbunden, Federungsund Dämpfungskomfort nur durch die Reifenfederungscharakteristik beeinflußbar.
   • 1.2 Fronträder von Gegengewichtsstaplern sind in gefederten Aufhängungen gelagert ( DE 100 62 565 A1 ).
   • 1.3 gefedertes Antriebsrad wird proportional zur aufgenommenen Last entlastet ( DE 919517 ).
2. 2. Vierradfahrwerk - statisch überbestimmt:
   • 2.1 alle Räder sind vertikal unbeweglich mit dem Rahmen verbunden, Federungsund Dämpfungskomfort nur durch die Reifenfederungscharakteristik und Radarmsteifigkeit beeinflußbar.
   • 2.2 gefederte Stützrolle in Kombination mit einem ungefederten Antriebsrad.
   • 2.3 gefedert gedämpfte Stützrolle in Kombination mit einem ungefederten Antriebsrad ( DE 298 01 892 U1 ).
   • 2.4 hydraulisch beaufschlagte / verriegelbare Stützrolle in Kombination mit einem ungefederten Antriebsrad ( DE 197 53 412 ).
   • 2.5 gefederte Stützrolle in Kombination mit gefederten Antriebsrad ( US 6,488,297 B2 ).
3. 3. Vierradfahrwerk - statisch bestimmt:
   • 3.1 Stützrolle und Antriebsrad sind kinematisch miteinander gekoppelt und werden durch eine Zusatzfeder beaufschlagt ( US 6,488,297 B2 ).
   • 3.2 Antriebs- und Stützrad befinden sich auf einer Trägereinheit, die auf einer Drehachse pendelnd zum Grundrahmen angeordnet sind. Trägereinheit und Grundrahmen sind zusätzlich mit Federelementen gekoppelt ( US 6,488,297 B2 ).
   • 3.3 Räder einer Fahrzeugachse sind mit Lenkern untereinander verbunden und beeinflussen sich gegenseitig.
   • 3.4 Trägereinheit von 3.2 und Lenker von 3.3 sind in Abhängigkeit von Betriebsparametern geometrisch verstell- und/oder verriegelbar.
4. 4. Fünfradfahrwerk
   • 4.1 vertikal unbewegliche Seitenstützrollen in Kombination mit einem vertikal beweglichen Antriebsrad, welches
     1. a) mit konstanter Federkraft auf den Boden gedrückt wird ( US 4,431,084 ).
     2. b) mit lastabhängiger Federkraft auf den Boden gedrückt wird ( EP 0 209 502 B1 ).
     3. c) mit lastabhängiger Hubkinematik auf den Boden gedrückt wird ( DE 3904798 A1 und DE 3904798 C2 ).
     4. d) in Abhängigkeit von Betriebsparametern auf den Boden gedrückt wird ( DE 3402495 , EP 0 329 504 B1 , GB 2094727 ).
     5. e) hubhöhenabhängig entlastet wird ( DE 3106027 A1 ).
   • 4.2 Vertikal unbewegliches Antriebsrad in Kombination mit vertikal beweglichen Stützrädern, welche unabhängig voneinander
     1. a) mit konstanter Federkraft auf den Boden gedrückt werden ( EP 0 480 817 , EP 0 329 504 , EP 2 606 765 ).
     2. b) mit einer Dämpfereinheit in Bodenkontakt stehen ( EP 0 584 704 ).
     3. c) mit einer Feder/Dämpfereinheit in Bodenkontakt stehen.
     4. d) hydraulisch beaufschlagt und/oder verriegelt werden.
   • 4.3 Vertikal unbewegliches Antriebsrad in Kombination mit vertikal beweglichen Stützrädern, welche abhängig kinematisch verbunden
     1. a) mit konstanter Federkraft auf den Boden gedrückt werden.
     2. b) mit einer Feder/Dämpfereinheit in Bodenkontakt stehen.
     3. c) mit einem Stellorgan wegab-unabhängig verriegelbar sind.
     4. d) mit einem Stellorgan lastabhängig auf den Boden gedrückt werden.

The above-described arrangement of the wheels in the vehicle frame of industrial trucks are divided into the following known chassis groups:

1. 1. Tricycle landing gear - statically determined:
   • 1.1 all wheels are vertically immovably connected to the frame, suspension and damping comfort influenced only by the tire suspension characteristics.
   • 1.2 Front wheels of counterbalanced trucks are stored in spring-loaded suspensions ( DE 100 62 565 A1 ).
   • 1.3 spring-loaded drive wheel is relieved proportionally to the recorded load ( DE 919517 ).
2. 2. Four-wheel drive - statically overdetermined:
   • 2.1 all wheels are vertically immovably connected to the frame, suspension and damping comfort influenced only by the tire suspension characteristics and Radarmsteifigkeit.
   • 2.2 spring-loaded support roller in combination with an unsprung drive wheel.
   • 2.3 sprung damped support roller in combination with an unsprung driving wheel ( DE 298 01 892 U1 ).
   • 2.4 hydraulically loaded / locked support roller in combination with an unsprung drive wheel ( DE 197 53 412 ).
   • 2.5 sprung support roller in combination with sprung drive wheel ( US 6,488,297 B2 ).
3. 3. Four-wheel drive - statically determined:
   • 3.1 support roller and drive wheel are kinematically coupled together and are acted upon by an additional spring ( US 6,488,297 B2 ).
   • 3.2 Drive and support wheel are located on a support unit, which are arranged on a rotation axis oscillating to the base frame. Carrier unit and base frame are additionally coupled with spring elements ( US 6,488,297 B2 ).
   • 3.3 Wheels of a vehicle axle are interconnected with links and influence each other.
   • 3.4 carrier unit of 3.2 and handlebar of 3.3 are geometrically adjustable and / or lockable depending on operating parameters.
4. 4. Five-wheel drive
   • 4.1 vertically immovable side support rollers in combination with a vertically movable drive wheel, which
     1. a) is pressed onto the ground with constant spring force ( US 4,431,084 ).
     2. b) is pressed to the ground with load-dependent spring force ( EP 0 209 502 B1 ).
     3. c) is pressed onto the ground with load-dependent lifting kinematics ( DE 3904798 A1 and DE 3904798 C2 ).
     4. d) is pressed onto the ground as a function of operating parameters ( DE 3402495 . EP 0 329 504 B1 . GB 2094727 ).
     5. e) depending on the lift height ( DE 3106027 A1 ).
   • 4.2 Vertically stationary drive wheel in combination with vertically movable support wheels which are independent of each other
     1. a) be pressed onto the ground with constant spring force ( EP 0 480 817 . EP 0 329 504 . EP 2 606 765 ).
     2. b) are in contact with a damper unit ( EP 0 584 704 ).
     3. c) with a spring / damper unit in contact with the ground.
     4. d) hydraulically applied and / or locked.
   • 4.3 Vertically stationary drive wheel in combination with vertically movable support wheels, which are kinematically linked
     1. a) be pressed with constant spring force to the ground.
     2. b) with a spring / damper unit in contact with the ground.
     3. c) are wegab-independent lockable with an actuator.
     4. d) are pressed with an actuator depending on the load on the ground.

The basis of all chassis design is the weighting of lateral stability of the vehicle and traction of the drive wheel. If the lateral stability in the foreground, so you designed the suspensions of the tilting wheels generating wheels rigid, this leads both in four-wheeled, as well as in five-wheeled vehicles to an over-determined Radaufstandssituation, which leads to traction problems on the drive wheel.

To obtain a defined drive wheel load, locked degrees of freedom of the wheel bearing must be reopened. This includes essentially in five-wheel vehicles, the vertical movement of the drive wheel suspension and four-wheel vehicles alternatively the vertically movable Seitenstützrad.
This also applies to kinematic couplings of the wheels of an axle or the formation of pendulum axles.

Vertical movable suspensions are supported by spring elements or hydraulic cylinders to the vehicle frame. With additional actuators at the o.g. Support elements can vary the respective wheel loads, which in turn has an impact on the wheel loads of the wheels vertically connected to the frame. Thus, as the drive wheel load increases, the wheel load of the side support rollers decreases on the same axle, in four-wheel drives the wheel loads of all wheels are affected.

Therefore, with increasing Antriebsradlast the lateral stability decreases, so that the vertically rigid connection of the suspension wheels of the tilting axis loses importance. There is a certain limit load, from which the inversion of the suspension "vertically fixed" to "vertically movable" and vice versa is mandatory, otherwise adjust to unstable driving conditions.

The vertically immovable drive wheel mates with vertically movable side support rollers, which are supported by springs and dampers to the vehicle frame, to avoid a dynamic swinging up when cornering. In this case, the majority of the entire drive axle load now rests in dependence on the weighting previously taken on the drive wheel, the so-called "load-oriented drive wheel". In borderline situations, vertical locking or resetting of the side support rollers to a base position can be controlled by operating parameters.

It can therefore be stated that at Fünfradfahrwerken at least one wheel per vehicle axle is carried out vertically immovable. This also applies to four-wheel drives with one exception (point 2.5 in accordance with US 6,488,297 B2 ), in which both drive wheel and support roller are supported separately via springs to the vehicle frame.

In the chassis embodiments described above, it is precisely the vertically immovable wheels of a vehicle axle that are decisive for the coordination between lateral stability and traction capability, as well as the dominant interface between road surface and vehicle frame excitation. The bumps of the ground are transferred undamped to the chassis. This manifests itself in disturbing noises, such as when driving over thresholds or the like. In addition, an undamped transmission of the shock takes place on the driver in the driver's seat or seat devices.

1. a) Fahrbahnstößen soll federnd ausgewichen werden.
2. b) hohes Dämpfungsvermögen für optimale dynamische Fahrstabilität.
3. c) keine negativen Auswirkungen auf die Fahrwerkseigenschaften: Seitenstabilität-Traktion.
4. d) Spurtreue und direkte Lenkeigenschaften.
5. e) geringe Lenkkräfte.
6. f) optimale Verschleisseigenschaften der Antriebsradbandage, besonders bei hohen Radlasten.
7. g) Minimierung von Fahrgeräuschen.
8. h) Minimierung des Rollwiderstandes.

The invention has for its object to provide a floor vehicle, in which the "load-oriented drive wheel" is so connected to the vehicle frame that the following properties are met:

1. a) Road shocks should be dodged resiliently.
2. b) high damping capacity for optimum dynamic driving stability.
3. c) no negative effects on the chassis characteristics: lateral stability traction.
4. d) Accuracy and direct steering characteristics.
5. e) low steering forces.
6. f) optimum wear characteristics of the drive wheel bandage, especially at high wheel loads.
7. g) Minimization of driving noise.
8. h) minimization of the rolling resistance.

If one examines the required properties with the solution potential of the known suspension components, the use of wheels with a particularly large deflection characteristic seems to be the obvious solution for the so-called "super-elastic tires" used in counterweight and reach trucks. So far, the use of these bandages limited only to the chassis types 1.1 and 2.1, all other chassis versions are equipped with polyurethane-tyred wheels, which have a very steep deflection characteristic compared to the "super-elastic wheel". To improve the traction properties and rubber bandages are used, however, have low carrying capacity and require high steering forces.

zu b):

Das Dämpfungsvermögen der Bandage steht in direkter Abhängigkeit vom Elastizitätsmodul, der die Federsteifigkeit mitbestimmt. Die Dämpfungskonstante ist somit nicht frei wählbar. Dieses hat zur Folge, daß die Abklingrate bei Fahrbahnstößen schlecht ist.

zu d):

Durch die für die gewünschte Federsteifigkeit große Bandagendicke verliert das Rad an Quer- und Verdrehsteifigkeit.

zu e):

das Schwenkmoment eines Rades ist proportional zur Radaufstandsfläche, diese wird um so größer je geringer die Bandagensteifigkeit ist.

zu f):

die Abriebfestigkeit bekannter "Super-Elastik-Räder" ist geringer , als bei markenüblichen Polyurethan-Rädern.

zu h):

der Rollwiderstand eines Rades ist proportional zur Radaufstandsfläche, dieser wird um so größer je geringer die Bandagensteifigkeit ist.

Only the above properties a), c) and g) are very well fulfilled by the "super-elastic tire", all others are much worse than the z. Currently used polyurethane wheels. The following reasons can be mentioned for this:

to b):

The damping capacity of the bandage is directly dependent on the modulus of elasticity, which determines the spring stiffness. The damping constant is thus not freely selectable. This has the consequence that the decay rate is poor in road shocks.

to d):

Due to the large thickness of the bandage required for the desired spring rigidity, the wheel loses its lateral and torsional rigidity.

to e):

The pivoting moment of a wheel is proportional to the wheel contact surface, this is the greater the lower the drum stiffness.

to f):

The abrasion resistance of known "super-elastic wheels" is lower than in conventional brand polyurethane wheels.

to h):

The rolling resistance of a wheel is proportional to the wheel contact surface, this is the greater the lower the drum stiffness.

The solution of the object of the invention is achieved by the features of claims 1 and 2.

In the truck according to the invention, the drive wheel via an additional spring arrangement with stiff spring characteristic and possibly special damper constant is supported on the chassis, which approximately represents the suspension behavior of an elastic tire, while the tires of the drive wheel is essentially unyielding. Industrial trucks, with the exception of counterbalanced trucks, which are also operated outdoors, usually have wheels with a polyurethane tire 90-93 Shore A, which is essentially inelastic.

Such tires are also provided in the drive wheel according to the invention. The spring arrangement is designed so that it does not give more than 2-10 mm at maximum load of the truck.

Since the drive wheel loads of the individual running gear designs are very different and thus also the wheel tire geometries have to be dimensioned individually, the following determination of the spring constants applies to the drive suspension according to the invention:

1. for chassis with load-dependent drive wheel pressure :

$$\frac{{\mathbf{F}}_{\mathbf{Drive\; wheel\; at\; rated\; load}\left[\mathbf{N}\right]}\mathbf{-}{\mathbf{F}}_{\mathbf{Drive\; wheel\; without\; load}\left[\mathbf{N}\right]}}{\mathbf{2}\left[\mathbf{mm}\right]}\mathbf{<}\mathbf{=}{\mathbf{C}}_{\mathbf{suspension}}\mathbf{<}\mathbf{=}\frac{{\mathbf{F}}_{\mathbf{Drive\; wheel\; at\; rated\; load}\left[\mathbf{N}\right]}\mathbf{-}{\mathbf{F}}_{\mathbf{Drive\; wheel\; without\; <figure-callout\; id="10"\; label="load\; N"\; filenames="imgf0001.png"\; state="\{\{state\}\}">load\; </figure-callout>}\left[\mathbf{N}\right]\left[\mathbf{}\right]}}{\mathbf{10}\left[\mathbf{mm}\right]}$$

2. for chassis with load-independent drive wheel pressure :

$$\frac{{\mathbf{F}}_{\mathbf{drive\; wheel}\left[\mathbf{N}\right]}}{\mathbf{2}\left[\mathbf{mm}\right]}\mathbf{<}\mathbf{=}{\mathbf{C}}_{\mathbf{suspension}}\mathbf{<}\mathbf{=}\frac{{\mathbf{F}}_{\mathbf{<figure-callout\; id="10"\; label="drive\; wheel\; N"\; filenames="imgf0001.png"\; state="\{\{state\}\}">drive\; wheel\; </figure-callout>}\left[\mathbf{N}\right]\left[\mathbf{}\right]}}{\mathbf{10}\left[\mathbf{mm}\right]}$$

In the invention, the spring characteristic of a super-elastic tire, as it is known in connection with industrial trucks, placed in the spring assembly and equipped the drive wheel itself with substantially unyielding tires. The possibility of variation of the spring constants of a spring has a great potential of individual tuning in comparison to the wheel tires.

The suspension-specific damping properties can now be realized just as individually by a separate damper, which acts on the drive wheel suspension. Since the invention relates to suspension axles with a load-oriented drive wheel, there is also the possibility, if there are still more wheels on the axle, which must now be performed compelling vertically movable to transmit the desired damping characteristic by arrangement of dampers on these wheels.

This is particularly advantageous because these wheels already have an independent spring / damper system, which only needs to be adjusted accordingly.

The invention is advantageously applicable to a tricycle, but it can also be used in the same advantageous manner for a five-wheel drive. In the latter case, it is expedient according to an embodiment of the invention, when the support wheels are supported on the chassis via a spring damping arrangement. The spring damping arrangement may be formed in a conventional manner, for example in the form that a relatively rigid working characteristic is provided in the supporting direction, while the relaxation characteristic of the damper is made flat. This means that under load, a high resistance is generated, while the extension of a support wheel after the previous retracting relatively no resistance and therefore quickly goes from stock, so that when retracting a support wheel when driving over a survey, the support wheel is quickly returned to the ground when the survey is abandoned.

In the invention, relevant effects on the ground clearance between the corridor and lower frame edge are eliminated. Furthermore, the cost of the frame of the vehicle is reduced, since this can be carried out constructively and in terms of its strength easier.

According to one embodiment of the invention, the support wheels can also be acted upon by a hydraulic or pneumatic adjusting cylinder, depending on operating parameters, such as pressure in the lifting cylinder, lifting height of the load, inclination of the pallet truck, acceleration or deceleration of the pallet truck, steering angle of the drive wheel, slip of the Drive wheel etc. to change the suspension characteristics.

However, the invention can also be applied in the same way to four-wheel trolleys.

Fig. 1

zeigt äußerst schematisch die Aufhängung eines Antriebsrads für ein Dreiradfahrwerk eines Flurförderzeugs.

Fig. 2

zeigt eine alternative Einzelheit von Fig. 1.

Fig. 3

zeigt äußerst schematisch das Antriebsrad eines Fünfradfahrwerks für ein Flurförderzeug mit beidseitigen Stützrollen.

Fig. 4

zeigt die Aufhängung einer Stützrolle des Fahrwerks nach Fig. 3.

Fig.

5 zeigt eine alternative Aufhängung einer Stützrolle des Fahrwerks nach Fig. 3.

Fig. 6

zeigt äußerst schematisch die Aufhängung eines Antriebsrad und einer Stützrolle bei einem Flurförderzeug mit Vierradfahrwerk.

The invention will be explained in more detail with reference to embodiments shown in the drawings.

Fig. 1

shows very schematically the suspension of a drive wheel for a tricycle chassis of a truck.

Fig. 2

shows an alternative detail of Fig. 1 ,

Fig. 3

shows very schematically the drive wheel of a five-wheel chassis for a truck with double-sided support rollers.

Fig. 4

shows the suspension of a supporting role of the chassis after Fig. 3 ,

FIG.

Figure 5 shows an alternative suspension of a support roller of the chassis Fig. 3 ,

Fig. 6

shows very schematically the suspension of a drive wheel and a support roller in a truck with four-wheel drive.

In Fig. 1 is indicated at 10, the chassis of a truck not shown, which has a tricycle landing gear. The front wheels are not shown, but only a drive wheel 12 on the longitudinal axis of the vehicle, which is driven by a motor-gear assembly 14 about a horizontal axis and is rotatably supported by a vertical shaft 16 about a vertical axis. The latter is done for steering purposes, as indicated by a double arrow 18. The steering is not shown. The shaft 16 is also limitedly displaced in the vertical direction and is guided in a suitable guide, thereby, which is not shown. Between the chassis 10 and the engine gear assembly 14, a spring assembly 20 is provided. This spring arrangement is designed so that it yields at maximum allowable load of the truck only a few millimeters, for example 3 to 6 mm. With the spring assembly 20, the behavior of a super elastic tire is essentially modeled, as it is otherwise used for drive wheels of industrial trucks. The drive wheel 12 also has a tire 22, which consists for example of Vulkollan and has extremely low compliance.

With a suspension, as in Fig. 1 is shown, the same behavior as in an elastic tire can be achieved without having to take over the disadvantages. A suspension, as in Fig. 1 is shown, has a high stability and better steerability of the drive wheel 12 than an elastic tire.

In Fig. 2 is indicated that in addition to the spring assembly 20, a damper 24 may be provided to absorb shocks on the drive wheel 12. The characteristic of the damper 24 may be such that the working characteristic is quite steep, while the relaxation characteristic is flat, so that the provision of the drive wheel 12 at a minimal retraction can occur relatively quickly, so that a constant contact with the ground is maintained.

In Fig. 3 a five-wheel chassis for a truck is indicated, in which the chassis 30 is in turn supported solely on the steerable drive wheel 12. (As far as the same parts as in the embodiment according to Fig. 1 are used, they are provided with the same reference numerals.) On both sides of the drive wheel 12 support rollers 32, 34 are arranged, which are rotatable both about a vertical and about a horizontal axis. This is well known for support rollers. In the present case, the support rollers 32, 34 are supported on the chassis 30 via a spring damping arrangement. Such is about in Fig. 4 indicated. It can be seen that the support roller 32 is articulated via a rocker 36 on the chassis 30, and the rocker 36 is supported by a spring 38 and a damper element 40 on the chassis. It is understood that the representation after Fig. 4 , as well as the after Fig. 5 only serves to explain and constructively can be performed in a variety of ways. The damper element 40 can be provided with a relatively steep working characteristic to effectively absorb shock or to stabilize the side of the vehicle effectively, without rolling movements must be feared. In the opposite direction (relaxation characteristic), the damper element 40 extends against a low resistance so that the spring 38 can always keep the support roller 32 in contact with the ground.

In the embodiment according to Fig. 5 a hydraulic cylinder 42 is disposed between spring 38 and chassis 30. The cylinder 42 is actuated by a controllable pressure source 44, which pressure may be dependent on a number of different parameters, for example the pressure in the lift truck, the lift of the loaded load, the truck tilt, the acceleration or deceleration of the vehicle, the steering angle of the drive wheel 12, the slip of the drive wheel 12, etc. This is indicated by the arrows 46 in FIG Fig. 5 indicated.

In Fig. 6 is a chassis 50 of a truck indicated with a four-wheel drive, with only a drive wheel 12 and a support wheel 34 are shown. The suspension of the Drive wheel 12 corresponds to that after the FIGS. 1 and 3 , therefore, like parts are given the same reference numerals. The support roller 34 is supported via a spring damping arrangement 52 on the chassis. The spring damping arrangement has approximately the effect, as determined by the FIGS. 4 and 5 has been described. In the embodiment according to Fig. 6 However, it should be noted that in contrast to the five-wheel drive after Fig. 3 the support roller 34 is designed in accordance with a load-oriented Antriebsraddruckes. About the spring 38, the division of the entire drive axle load on the drive wheel 12 and support wheel 34 is controlled. Decisive here is the required drive wheel pressure for starting and braking under nominal load.

Claims (6)

1. An industrial truck with a travel drive which drives a single driving wheel which also is pivotally supported, as a steered wheel, about a vertical axis, wherein at least one side of the driving wheel (12) or the same axle of the driving wheel (12) has disposed thereon a supporting wheel (32, 34), and the driving wheel (12) of an industrial truck featuring a load-dependent driving axle load is supported on the chassis via a spring assembly, characterized in that the spring constant of the spring assembly (20) is fixed as follows: $$\frac{{\mathbf{F}}_{\mathrm{Driving\; wheel\; at\; a\; rated\; load}\left[\mathrm{N}\right]}\mathrm{-}{\mathbf{F}}_{\mathrm{Driving\; wheel\; at\; no\; load}}\left[\mathbf{N}\right]}{\mathrm{2}\left[\mathrm{mm}\right]}\mathrm{<}\mathrm{=}{\mathbf{C}}_{\mathrm{Spring\; system}}\mathrm{<}\mathrm{=}\frac{{\mathbf{F}}_{\mathrm{Driving\; wheel\; at\; a\; rated\; load}\left[\mathrm{N}\right]}\mathrm{-}{\mathrm{F}}_{\mathrm{Driving\; wheel\; at\; no\; load}}\left[\mathbf{N}\right]}{\mathrm{2}\left[\mathrm{mm}\right]}$$

   

   
   where F is the respective contact pressure force of the driving wheel (12), and the driving wheel (12) having a a non-compliant tyre, and that the supporting wheel (32, 34) being freely pivotable about a vertical axis and vertically movable is supported on the chassis via a spring-actuated cushioner assembly.
2. An industrial truck with a travel drive which drives a single driving wheel which also is pivotally supported, as a steered wheel, about a vertical axis, wherein at least one side of the driving wheel (12) or the same axle of the driving wheel (12) has disposed thereon a supporting wheel (32, 34), and the driving wheel (12) of an industrial truck featuring a load-independent driving axle load is supported on the chassis via a spring assembly, characterized in that the spring constant of the spring assembly (20) is fixed as follows: $$\frac{{\mathbf{F}}_{\mathbf{Driving\; wheel}}\left[\mathbf{N}\right]}{\mathbf{2}\left[\mathbf{mm}\right]}\mathbf{<}\mathbf{=}{\mathbf{C}}_{\mathbf{Spring\; system}}\mathbf{<}\mathbf{=}\frac{{\mathbf{F}}_{\mathbf{Driving\; wheel}}\left[\mathbf{N}\right]}{\mathbf{10}\left[\mathbf{mm}\right]}$$

   

   
   where F is the respective contact pressure force of the driving wheel (12), and the driving wheel (12) having a a non-compliant tyre, and that the supporting wheel (32, 34) being freely pivotable about a vertical axis and vertically movable is supported on the chassis via a spring-actuated cushioner assembly.
3. The industrial truck according to claim 1 or 2, characterized in that the spring assembly (20) has associated therewith a cushioner assembly (24).
4. The industrial truck according to claim 1, 2 or 3, characterized in that a supporting wheel disposed on the axle of the driving wheel is provided with a cushioner assembly and the cushioning action for the driving wheel is assumed by the cushioner assembly of the supporting wheel.
5. The industrial truck according to any one of claims 1 to 4, characterized in that the compliance of the spring assembly (20) is not superior to from 3 to 6 mm at a maximum permissible load.
6. The industrial truck according to claims 1 to 5, characterized in that the supporting wheel (32) is acted on by a power-driven setting member (42) which is controllable by one or more operation parameters of the industrial truck for a variation of the end-bearing force of the supporting roller (32).

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